To change your name in the leaderboard event, you can do the following:

1. Start the game.
2. If it's the first time you see the leaderboard event, the tutorial will have a step to select your name.
3. If it's not the first time you see the leaderboard event, you can:
   1. Tap on the leaderboard Icon in the objective bar.
   2. Find your name.
   3. Tap on the small pencil next to your profile picture.
   4. Change your name and save.